Pre-charging control strategies of modular multilevel converter

Based on a novel multilevel voltage source converter (VSC) used for electric drive, the pre-charging process of the converter is fully analyzed, so as to find a suitable pre-charging control strategy. For a single converter with redundant modules, the process is divided into two stages, the unlock charging course is in particular analyzed. To ensure the normal operation of the converter, an optimized charging method is presented. For a modular multilevel converter system used as rectifier side and inverter side, the pre-charging control strategy is separately analyzed and proved to be suitable and effective.